For many years, aluminum alloying systems have been successfully used in self shielded flux cored welding electrodes to produce weld deposits with exceptional impact and strength properties. Exceptional mechanical properties can be developed when using self shielding flux cored welding electrodes when the deposited weld metal has an aluminum content of approximately 0.5%. It is believed that the aluminum forms a nitride which precipitates in the metal of the weld bead and enhances the mechanical properties of the weld metal. The aluminum is employed for alloying with the weld metal to remove oxygen and free nitrogen from the solidified weld bead. In the well developed specialized technology used to create self shielded flux cored welding electrodes, the use of aluminum to alloy with the weld bead metal has resulted in a weld bead alloy about 0.5 to 1% aluminum. With this alloy composition, the aluminum nitride is formed and free nitrogen is not generally available. As the amount of alloyed aluminum was decreased in the weld metal, it was found that the porosity of the weld metal increased to decrease the strength and impact characteristics of the weld joint. Consequently, it was believed that when aluminum was used as an alloying agent for the weld metal in self shielded welding, it was necessary to create more than 0.5% aluminum in the weld metal. This use of an aluminum for the controlling properties of the weld bead allowed the aluminum to interact within the weld bead as an alloying constituent. Since the electrode was self shielding, the gases created by the arc expelled air and prevented oxygen and nitrogen from ingressing into the molten metal due to the rapid egress of gas created by the arc. Thus, there was no reaction zone in the arc in which the aluminum was primarily reacted with other constituents. The aluminum entered the weld bead and alloyed with the metals of the weld bead.
When using gas shielded flux cored arc welding electrodes as contemplated by the present invention, deoxidation of the weld metal or control of nitrogen in the weld metal is not primarily dependent on aluminum. These particular electrodes are primarily carbon-manganese-silicon type systems which rely on the gas shielding to prevent nitrogen contamination of the weld pool metal by excluding the surrounding atmosphere. Manganese and silicon are used as alloying agents for deoxidizing or killing the metal in the weld metal bead. The use of aluminum of any type in gas shielded electrodes, which is not a concept employed in practice, has merely been suggested as one of many possible means of alloying the weld metal. There has been no suggestion of using aluminum for reaction in the reaction zone of the arc above the weld metal pool in an electric arc welding process of the type using shielding gas. Consequently, electrodes used in arc welding with shielding gas intentionally avoided aluminum in the weld metal deposit believing that this lack of aluminum in the deposit would assist in providing better mechanical properties. In the past, the use of aluminum alloying agent for a gas shielded electrode was not used in practice, and the weld metal generally had no aluminum in the weld metal. This was believed to assure better strength and impact characteristics. There was no effort to use aluminum as an alloying agent in the weld bead when using shielded gas type of flux cored electrodes.